Nail disorders in children — formative SAQs

SAQ 1 (10 marks)

A 9-year-old boy is referred with an 18-month history of a progressively thickened, yellow, crumbly left great toenail. His father has tinea pedis and a thickened toenail. The nail shows subungual hyperkeratosis and distal onycholysis. No mycology has been done. The family asks for tablets to clear it. [4]

Question: (a) What is the likely diagnosis, and what must you do to confirm it before any systemic treatment, and why? (b) Outline the stepwise management once confirmed, including a specific drug, dose and duration. (c) What else should you address, and what are the red flags in a child with a disordered nail? (10 marks) [1]

Model answer

(a) Diagnosis and confirmation (3 marks). The likely diagnosis is onychomycosis — a thickened, discoloured, crumbly nail with subungual hyperkeratosis and distal onycholysis, in a child with a household contact (his father), which is a recognised transmission risk. Before any systemic treatment, confirm with mycology: take subungual debris from the most proximal active edge for potassium hydroxide examination plus fungal culture, or polymerase chain reaction where available. The reason is practical and safety-driven — the clinical appearance overlaps with psoriasis and trauma, and systemic antifungals carry hepatic and drug-interaction risk, so a child should not receive them on appearance alone. [4] [1]

(b) Stepwise management (4 marks). Once confirmed, the ladder runs from topical to systemic. For limited distal disease, a topical agent such as amorolfine or efinaconazole applied over many months may suffice. For extensive disease like this (a whole great toenail over 18 months), first-line systemic therapy for dermatophyte infection is weight-based oral terbinafine: under 20 kg at 62.5 mg once daily, 20 to 40 kg at 125 mg once daily, and over 40 kg at 250 mg once daily, given for about 12 weeks for a toenail, with liver-function monitoring. Itraconazole is a specialist alternative. Set the family's expectation that a normal-looking toenail is 12 to 18 months away because of the slow growth rate, and treat the father's tinea pedis to reduce reinfection. [4] [3]

(c) Associated measures and red flags (3 marks). Address the household transmission by treating affected contacts, reinforce footwear hygiene, and explain the long regrowth time to support adherence. The red flags that must not be missed in any child with a disordered nail are a progressive, widening or darkening longitudinal melanonychia in a single nail of a fair-skinned child (possible nail melanoma), a destructive subungual lesion with bone involvement (possible exostosis or malignancy), and scarring nail lichen planus with a pterygium that threatens permanent matrix loss. If mycology is negative, reconsider nail psoriasis and trauma rather than escalating empirically. [1] [7] [5]

SAQ 2 (10 marks)

Question: A 15-year-old boy presents with a third episode in a year of an ingrown left great toenail, with a painful, erythematous, swollen lateral nail fold and visible granulation tissue but no spreading redness or systemic symptoms. (a) Outline your assessment and the conservative management you would start. (b) When would you use antibiotics, and what surgical option is there for recurrent disease? (c) What advice prevents recurrence, and how does this differ from managing acute paronychia? (10 marks) [3]

Model answer

(a) Assessment and conservative care (4 marks). This is a recurrent ingrown toenail (onychocryptosis) — pain, erythema and swelling of the lateral fold of the great toe with granulation tissue, commonest in adolescents and driven by tight footwear, incorrect curved nail trimming and hyperhidrosis. Confirm there is no spreading infection (redness tracking toward the toe) or systemic upset. Conservative management first: warm antiseptic soaks, proper square (not curved) nail trimming, a cotton-wisp or taping technique to lift the offending lateral edge off the inflamed fold, footwear change to a wide toe box, and advice to avoid digging at the nail. Most early and even recurrent episodes settle with these measures. [3] [1]

(b) Antibiotics and surgery (3 marks). An oral antibiotic is reserved for genuinely spreading infection (redness tracking toward the toe, lymphangitis, or systemic symptoms) or an immunocompromised child — not for simple inflammation, because the problem is usually mechanical. For recurrent or severe disease that has failed conservative care, as here, the surgical option is wedge excision of the lateral nail edge with phenol matrixectomy (applying phenol to the lateral horn of the matrix to prevent regrowth), which gives a low recurrence rate. Drain any pointing abscess at the time of surgery. [3] [1]

(c) Prevention and the contrast with paronychia (3 marks). Recurrence is prevented by square trimming (cutting the nail straight across, not into the corners), a wide toe-box shoe, keeping the feet clean and dry, and avoiding trauma to the nail fold. This contrasts with acute paronychia, which is a staphylococcal infection of a finger nail fold (not a toe, and not primarily mechanical): its key step is drainage of a pointing abscess with a small nick, with an anti-staphylococcal beta-lactam such as flucloxacillin or cephalexin added if infection is spreading. The ingrown toenail is managed by lifting the nail edge; paronychia is managed by draining the fold. [3] [1]